The invention relates to a cross arm mechanism in a pushbutton tuner.
In a pushbutton turner, a setting plate mounted on a cross arm is rotatable and is changeable in its fixed angle to vary the moving distance of a memory slide to be pushed by the setting plate and to further have a core interlocking with the memory slide advance up to a given position in a tuning coil, thereby selecting a desired waveband.
To fix the setting plate at a desired angle on the cross arm in such a pushbutton tuner, a structure as shown in FIG. 1 has conventionally been adopted. Namely, the setting plate 3 is pivotally mounted at one end thereof on the cross arm 1 by means of a pin 2. The other end of the setting plate is pressed downwardly by a plate spring 4 so as not to rotate when tuning is done. Such conventional mechanism, however, is arranged to press the setting plate from above and accordingly requiring of a setting pin 5 of a considerable height pressing the plate spring 4 downwardly so to ensure its function as a spring, makes whereby the cross arm is relatively thick as a whole.
In this connection, in accordance with the recent necessity of thinning pushbutton tuners, the above-mentioned conventional mechanism as shown in FIG. 1 has been replaced by a new mechanism as shown in FIG. 2 in which the setting plate is fixed by applying a grasping force from the lateral sides thereof. Namely, the setting plate 13 is pivotally mounted on the cross arm 11 by means of a setting pin 12 having a flange at the top end thereof. The setting plate 13 has a cylindrical boss 14 integrally formed at lower portion thereof. The boss 14 is surrounded by a plate spring 15 in a U-like configuration which grasps the boss 14 from the right and left directions when a pushbutton advances so as not to permit the setting plate 13 to rotate about the setting pin 12. Such mechanism certainly contributes to a reduction of the thickness of the cross arm mechanism as a whole as compared with that as shown in FIG. 1. However, when practically adopting it, there has been a drawback: because the setting plate 13 has to be pivotal with respect to the setting pin 12, there must be provided a clearance between the setting pin 12 and the shaft bore of the setting plate 13. This sometimes causes discrepancy of its center line depending on whether it is freely rotatable or is fixed by the plate spring. Such discrepancy of its center line makes it impossible to precisely determine the position of the setting plate corresponding to wavebands to be selected and causes frequency deviation. This causes deterioration of performance of the pushbutton tuner.